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xen: multiple vulnerabilities

Package(s):xen CVE #(s):CVE-2014-1891 CVE-2014-1892 CVE-2014-1893 CVE-2014-1894 CVE-2014-1896
Created:February 12, 2014 Updated:February 25, 2014
Description: From the Xen advisories [1, 2, 3]:

[1] The FLASK_{GET,SET}BOOL, FLASK_USER and FLASK_CONTEXT_TO_SID suboperations of the flask hypercall are vulnerable to an integer overflow on the input size. The hypercalls attempt to allocate a buffer which is 1 larger than this size and is therefore vulnerable to integer overflow and an attempt to allocate then access a zero byte buffer. (CVE-2014-1891)

Xen 3.3 through 4.1, while not affected by the above overflow, have a different overflow issue on FLASK_{GET,SET}BOOL (CVE-2014-1893) and expose unreasonably large memory allocation to arbitrary guests (CVE-2014-1892).

Xen 3.2 (and presumably earlier) exhibit both problems with the overflow issue being present for more than just the suboperations listed above. (CVE-2014-1894 for the subops not covered above.)

The FLASK_GETBOOL op is available to all domains.

The FLASK_SETBOOL op is only available to domains which are granted access via the Flask policy. However the permissions check is performed only after running the vulnerable code and the vulnerability via this subop is exposed to all domains.

The FLASK_USER and FLASK_CONTEXT_TO_SID ops are only available to domains which are granted access via the Flask policy.

Attempting to access the result of a zero byte allocation results in a processor fault leading to a denial of service.

[2] The FLASK_AVC_CACHESTAT hypercall, which provides access to per-cpu statistics on the Flask security policy, incorrectly validates the CPU for which statistics are being requested.

An attacker can cause the hypervisor to read past the end of an array. This may result in either a host crash, leading to a denial of service, or access to a small and static region of hypervisor memory, leading to an information leak.

[3] libvchan (a library for inter-domain communication) does not correctly handle unusual or malicious contents in the xenstore ring. A malicious guest can exploit this to cause a libvchan-using facility to read or write past the end of the ring.

libvchan-using facilities are vulnerable to denial of service and perhaps privilege escalation.

Alerts:
Gentoo 201407-03 xen 2014-07-16
openSUSE openSUSE-SU-2014:0483-1 xen 2014-04-04
SUSE SUSE-SU-2014:0446-1 Xen 2014-03-25
SUSE SUSE-SU-2014:0373-1 Xen 2014-03-14
SUSE SUSE-SU-2014:0372-1 Xen 2014-03-14
CentOS CESA-2014:X007 xen 2014-02-25
Fedora FEDORA-2014-2188 xen 2014-02-16
CentOS CESA-2014:X004 xen 2014-02-12
Fedora FEDORA-2014-2170 xen 2014-02-16

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